Call SOAP service using locally available WSDL

Hello Appian practitioners, 

Following the notes from this discussion,

I tried creating a WEB-API to load a locally available WSDL within the 'Call Web Service' smart service.

My web-api returns the following httpResponse

a!httpResponse(
/*
* Set an HTTP header that tells the client that the body of the response
* will be a CSV attachment.
*/
headers: {
a!httpHeader(
name: "Content-Disposition",
value: "attachment; filename=" & char(34) & local!username & ".xml" & char(34)
)
},
/*
* Create a CSV value of 'local!user' and place it in the response body.
*/
body: rule!TS_test_ProfileXML() /* XML Contents */
)

However, the call web-service is still not able to detect the WSDL. 

Appreciate all your help!